Soap-salt complex thickened grease compositions



Unite States Patent Arnold J Morway, Clark, N. "J., assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. pplication April 1a, 1955 Serial No. 502,519

7 Claims. ((31. 252-435 This invention relates to new and improved lubricating grease compositions. More particularly, the invention pertains to lubricating oil base stocks thickened to grease consistency with soap-salt complexes comprising a metal salt of'low molecular weight carboxylic acids, a metal salt of an alkylene diamine tetra carboxylic acid, and a metal soap of high molecular weight carboxylic acids.

In brief compass, the present invention relates to compositions consisting of or containing complex compounds consisting of a metal salt of a low molecular weight carboxylic acid containing from about 1 .to 3 carbon atoms per molecule, a metal salt of an ethylene diamine tetra aliphatic carboxylic acid containing 1 to 4 carbon atom-s in theali'phatic acid group and a metal soap of a high molecular weight carboxylic acid containing from about 12 to 30 carbon atoms per molecule. Grease compositions containing the complex compounds of the invention havebeen found to be suitable for lubricating services operating over 'a broad range of temperatures and under conditions of'high unit load or boundary lubricating conditions.

The use of soap-salt complexes as grease thickeners is well known in the art. The complex compounds used heretofore consisted of combinations of metal soaps of high molecular weight carboxylic acids and metal salts of low molecular weight carboxylic acids. The com monly known grease-making, high molecular Weight fatty acids, saturated or unsaturated, having from 12 to 22 carbon atoms have been employed in conjunction with such low molecular weight carboxylic acids, as acetic, propionic aljkoxy propionic and the like to form the complex grease thickeners of the prior art.

lnU. S. Patent No. 2,680,094, issued to Bartlett et al., the use of esters or metal salts of esters of ethylene bisimino aliphatic carboxylic acids, i. e. ethylene diamine tetraaliphatic carboxylic acids, are disclosed as rust inhibiting lubricating oil additives. The preparation of the rust preventive additives of the Bartlett et al. patent involved esterifying the nitrogen-containing complex acids with aliphatic alcohols having between about 4 and 18 carbon atoms per molecule.

It has now .beenfound that metal .salts of alkylene diamine tetra aliphatic carboxylic acids having from'l to 4 carbon atoms in the aliphatic carboxylic acid group can be utilized in conjunction with metal salts of low molecular weight carboxylic acids and metal soaps of high molecular weight carboxylicacids to preparesoapsalt complexes capable of thickening lubricating oils to grease consistency and imparting excellent load carrying characteristics to the final grease composition. By 'em- "ice ploying the alkylene diamine tetra carboxylic acids there is obtained a high combined metal content in the grease compositions with extremely high load carrying abilities Without employing large amounts of salts and soaps. It has also been found that grease prepared in accordance with the invention will still retain adequate load carrying properties after they have been diluted or blended to make softer greases. i

The low molecular weight carboxylic acids contemplated in this invention include saturated and unsaturated monocarboxylic acids having from about .1 to 3 carbon atoms per molecule, such as formic, acetic, propionic, lactic, acrylic and similar acids. Acetic acid is especially preferred and may be employed in the form of glacial acetic acid or concentrated aqueous solution containing from about 60 to 99.9 wt.percent, preferably about wt. percent, of acetic acid. In general, the low molecular weight carboxylic acid employed should have a saponification value ofabove about 600, preferably about 900.

Suitable 'high molecular weight carboxylic acids are those containing from about 12 to 30 carbon atoms, preferably from aboutl8 to 22 carbon atoms, per molecule. These acids may be derived from saturated or unsaturated naturally occurring or synthetic fatty material. Thefatt-y acids normally used in the manufacture of conventional grease thickeners, particularly the more saturated acids, are preferred. Examples of such acids include lauric, 'myristic, palmitic, stearic, mono-hydroxy stearic, di-hydroxy stearic, 'poly-hydroxy stearic, arachidic, hydrogenated fish oil, tallow acids, 'etc. However, unsaturated acids such as oleic, ricinoleic and similar acids may also be employed. The average saponification value of the high molecular weight monocarboxylic acids useful for the purposes of the present invention should not be more than about 300, preferably not more than about 220.

The nitrogen-containing complex acids, suitable for the purposes of this invention are the alkylene diamine tetra aliphatic carboxylic acids having the following approximate formula Hooon nooon NCHzCH;N

' H OOC/ R RCOOH wherein R is an alkyl group having from 1 to 4 carbon atoms. Eethylene bis-imino diacetic acid is commercially available from the -Alrose Chemical Co. under the trade name sequestrene AA. The tetraor trisodiurn salts are also commerciallyavailable under the trade name Versene from the Bersworth Chemical Co. Although ethylene diamine tetra acetic acid is preferred, the acids may be derived from :other low .molecular weight aliphaticcarbox-ylic acids having from 1 to 4 carbon-atoms per molecule.

V The choice of metalcomponent .dependsto a certain extent on the use of the soap-saltcomplexes of the invention. The alkaline earth metals such as calcium, barium, strontium and magnesium are I particularly useful for many purposes of the invention. Calcium is especially preferred. 'These metals afford the greatest advantages when thesoap-salt complexes are used as grease thickeners, since they result in the production of greases having outstanding load carrying characteristics even without the use of conventional extreme pressure agents.

The metal components of the salts and soaps may be any one or more of the metals set forth above. In most cases, however, the salts and soaps contain the same metal or comlination of metals.

The soap-salt complexes of the invention may be utilized in combination with a wide variety of mineral as Well as synthetic lubricating oils. Relatively large proportions of active metal may thus be introduced into the oils without solubility problems. Mineral base lubricating oils ranging in viscosity from about 50 to 2000 S. U. S. at 100 F., 35 to 100 S.'U. S. at 210 F., are preferably employed as the liquid phase of the grease compositions of the invention. These naturally occurring mineral lubricating oils may be derived from any crude source, whether paraflinic or naphthenic in origin, which are refined by any of the well known refining techniques.

The invention is not limited, however, to the use of mineral base oils, since various synthetic oils may also be used as part or all of the liquid phase of the grease. Examples of operable synthetic oils include ether alcohols, such as those corresponding to the general formula RO (C H O) H noyl, decyl, lauryl, stearyl and similar radicals; diesters of dibasic acids, such as adipic or sebacic acid with monohydric alcohols, such as hexyl, octyl, Z-ethyl hexyl or higher alcohols; esters of polyethylene glycols with C to C branched-chain carboxylic acids; complex esters of polybasic carboxylic acids, polyhydric alcohols, monobasic acids and/or monohydric alcohols, such as the well known glycol-centered or dibasic acid-centered complex esters; phosphoric acid esters of thioesters of aliphatic alcohols or mercaptans of up to about 18 carbon atoms; halocarbon oils, such as the polymers of chlorofluoro alkylenes like chlorotrifluoroethylene; organo-siloxanes; sulfite esters; organic carbonates; mercaptals; formals; etc.

In general, greases containing the thickeners of this invention areprepared by dispersing high molecular weight fatty acids and alkylene diamine tetra carboxylic acid with metal base in a portion or all of the lubricating oil to be used in the grease. The mixture is then heated to a temperature of about 80 to 130 F. with mixing. The low molecular weight carboxylic acid is then added. If only a portion of the lubricating oil was added initially, the remaining portion can be added at this point along with the low molecular weight carboxylic acid. Heating is continued to a temperature of about 400 to 550 F. The heating is then discontinued, and the grease batch cooled to a temperature of about 200 to 250 F. with agitation. At this temperature any of the conventional grease additives, e. g. oxidation inhibitors, such as phenyl alpha naphthylamine, can be added. The grease batch is then cooled to a temperature below about 180 F., and Gaulin homogenized.

The grease compositions of the invention can also be prepared by coneutralizing all of the carboxylic acids employed in situ in the liquid menstruum to which the complex compound is to be applied in actual use.

The soap-salt complexes may also be prepared by separately preforming at least a portion of either the metal salt of the low molecular weight carboxylic acids, the metal salt of the ethylene diamine tetra carboxylic acids or the metal soap of the high molecular weight carboxylic acids. This method is particularly useful when different metals are employed as the metal constituents of the salts and soaps.

When the soap-salt complexes are preparedin a liquid dispersant or solvent, they may be isolated by solvent extraction of the dispersing medium in a solvent in which the complex is insoluble. Suitable solvents include acetone, ether, hexane, etc.

As previously mentioned, the lubricating grease compositions of the invention can be diluted or blended with from about 10 to 70 wt. percent, preferably 25 to 50 wt. percent, of a mineral or synthetic lubricating oil to make softer greases having excellent load carrying characteristics.

In preparing the lubricating grease compositions of the invention about 50 to 97 wt. percent of lubricating oil and about 3 to 50 wt. percent of soap-salt complex are employed. The preferred grease compositions contain from about 5 to 30 wt. percent of the soap-salt complex containing from about 5 to 20 wt. percent of a low molecular weight carboxylic acid, from about 1 to 5 wt. percent of an ethylene diamine tetra carboxylic acid and from about 3 to 15 wt. percent of high molecular weight carboxylic acids. Thus, the complex itself is formed from 1 to 5 parts by weight of the ethylene diamine terta carboxylic acid, 5 to 20 parts by weight of the low molecular weight carboxylic acid, and 3 to 15 parts by weight of the high molecular weight carboxylic acid. The amount of metal base employed will ordinarily be within the range of about 5 to 15 wt. percent, all of the above weight percentages being based on the total weight of the final grease compositions.

The invention will be more fully understood by reference to the following example, which illustrates various modifications of the invention:

EXAMPLE Composition A Composition B All of the mineral lubricating oil, hydrated lime, stearic acid and ethylene diamine tetra acetic acid were charged to a fire heated kettle and warmed to about F. with stirring. The acetic acid was then added, and heating continued to a temperature of about 500 F. Heating was then discontinued, and the grease mixture cooled to about 250 F. with agitation. At this temperature phenyl alpha naphthylamine was added, the resulting grease mixture cooled to a temperature below about 180 F., and then Gualin homogenized at 6500 p. s. i.

Composition C This grease composition was prepared by blending about 75 wt. percent of Grease B with about 25 wt. percent of a mineral lubricating oil having a viscosity of 70 SUS at 210 F. at a temperature of about 200 F.

Composition D This grease composition was prepared by blending about 75 wt. percent of Grease A with about 25 wt. percent of a mineral lubricating oil having a viscosity of 70 SUS at 210 F. at a temperature of about 200 F.

. characteristics.

TABLE Grease Composition No A B O D Formulation (W t. percent):

Glacial acetic acid 8.0 12. 9. 0 6. 00 Btearic acid 4. 0 4. 0 3. 0 3. 00 Ethylene diamine tetra acetic acid- 2. 0 1. Hydrated lime 6. 0 10. 0 7. 5 4. 50 Phenyl alpha naphthylamine 0. 5 0. 5 0. 375 0. 375 Mineral lubricating oil- 55 SUS at 210F--- 81.5 71.5 53. 625 61.125 70 BUS at 210F.-- 25. 25. 00 Properties:

Appearance Smooth, uniform, short fiber Dropping Point (F.) 500+ 500+ 500+ 500+ Penetrations (77F. min/1 Unworked 262 245 310 315 Worked 60 strokes 292 285 315 330 Worked 100,000 strokes (125F.)- 340 245 Cooled to 77F.-60 additional strokes 339 325 Wheel Bearing Test (220F. 6 hours 660 R. P. M.) Pass Pass Tlmken Test (lb. load) 30 Fail 60 (nar- 40 (nar- 30 Fail row scar) row scar) Norma Hoffman Oxidation Test (hrs. to 5 p. s. i. o 365 385 Lubrication Liie (hrs (250F.10,000

R. P. M.) 2, 100 2, 200 Water Solubility Nil It will be noted that Grease B has an outstanding load carrying ability in addition to other desirable grease Furthermore, when Grease B is diluted or blended with additional lubricating oil it retains an adequate load carrying ability although the grease is softer in structure. When Greases B and C, the preferred lubricating grease compositions of the invention, are compared to Greases A and D, the new and unexpected results of this invention are clearly indicated.

The invention is not limited to the specific conditions and materials of the foregoing example. These conditions and materials may be varied within the limits indicated in the general portions of the specificaton. The grease compositions prepared in accordance with the invention may also contain various conventional additives such as oxidation inhibitors, metal deactivators, corrosion inhibitors, extreme pressure agents, etc. as will be understood by those skilled in the art.

What is claimed is:

l. A soap-salt complex comprising a metal salt of a low molecular weight monocarboxylic acid having in the range of 1 to 3 carbon atoms per molecule, a metal salt of an ethylene diamine tetra aliphatic carboxylic acid, the carboxylic groups thereof having in the range of 1 to 4 carbon atoms, and a metal soap of a high molecular weight carboxylic acid having in the range of 12 to 30 carbon atoms per molecule, said complex being formed at a complex-forming temperature in the range of 400-550 F. and containing in the range of 5 to 20 parts by weight of said low molecular weight monocarboxylic acid, 1 to 5 parts by weight of said ethylene diamine tetra aliphatic carboxylic acid, and 3 to 15 parts by weight of said high molecular weight carboxylic acid, and the metal constituent of said metal salts and soap, being an alkaline earth metal.

2. The complex of claim 1 wherein said ethylene diamine tetra aliphatic carboxylic acid is ethylene diamine tetra acetic acid, and said low molecular weight monocarboxylic acid is acetic acid.

.3. A lubricating grease composition comprising a mineral lubricating oil thickened to a grease consistency within the range of 3 to 50 wt. percent of a soap-salt complex consisting of a metal salt of in the range of 5 to wt. percent of a low molecular weight monocarboxylic acid having in the range of 1 to 3 carbon atoms per molecule, a metal salt of in the range of 1 to 5 wt. percent of an ethylene diamine tetra aliphatic carboxylic acid, the carboxylic acid groups thereof having in the range of 1 to 4 carbon atoms, and a metal soap of in the range of 3 to 15 wt. percent of a high molecular weight carboxylic acid having in the range of 12 to 30 carbon atoms per molecule, the weight percentages being based on the total grease composition, the metal constituent of said metal salts and soap being an alkaline earth metal and said complex being formed at a complex-forming temperature in the range of 400 to 550 F.

4. The grease composition of claim 3 wherein said low molecular weight monocarboxylic acid is acetic acid.

5. The lubricating grease composition of claim 3 wherein said alkaline earth metal is calcium.

6. The process of preparing a lubricating grease composition which comprises dispersing in a mineral lubri cating oil in the range of 3 to 15 wt. percent of a high molecular weight carboxylic acid having in the range of 12 to 30 carbon atoms per molecule, in the range of 1 to 5 wt. percent of an ethylene diamine tetra aliphatic carboxylic acid, the carboxylic acid groups thereof having in the range of 1 to 4 carbon atoms, and in the range of 5 to 15 wt. percent of an alkaline earth metal base, heating the resulting dispersion to a temperature in the range of to F., then adding in the range of 5 to 20 wt. percent of a low molecular weight monocarboxylic acid having in the range of 1 to 3 carbon atoms per molecule, continuing heating the mixture to a complex-forming temperature in the range of 400 to 550 F., and then cooling the mixture to obtain said lubricating grease composition.

7. The process of claim 6 wherein said ethylene diamine tetra aliphatic carboxylic acid is ethylene diamine tetra acetic acid, wherein said low molecular weight monocarboxylic acid is acetic acid, and wherein said alkaline earth metal is calcium.

References Cited in the file of this patent UNITED STATES PATENTS 2,197,263 Carmichael et a1. Apr. 16, 1940 2,240,957 Munz May 6, 1941 2,412,944 Bersworth Dec. 24, 1946 2,417,428 McLennan' Mar. 18, 1947 2,564,561 Carmichael et al. Aug. 14, 1951 2,583,607 Sirianni et al. Jan. 29, 1952 2,628,195 Allison et al. Feb. 10, 1953 OTHER REFERENCES The Institute Spokesman, vol. 14, No. 12, March 1951 (Amott and McLennan Article), pages 7-23.

Boner: Lubricating Greases, chapter 16, page: 615- 675, Reinhold Pub. Corp., New York, N Y. 

3. A LUBRICATING GREASE COMPOSITION COMPRISING A MINERAL LUBRICATING OIL THICKENED TO A GREASE CONSISTENCY WITHIN THE RANGE OF 3 TO 50 WT. PERCENT OF A SOAP-SALT COMPLEX CONSISTING OF A MATAL SALT OF IN THE RANGE OF 5 TO 20 WT. PERCENT OF A LOW MOLECULAR WEIGHT NONOCARBOXYLIC ACID HAVING IN THE RANGE OF 1 TO 3 CARBON ATOMS PER MOLECULE, A METAL SALT OF IN THE RANGE OF 1 TO 5 WT. PERCENT OF AN ETHYLENE DIAMINE TETRA ALIPHATIC CARBOXYLIC ACID. THE CARBOXYLIC ACID ATOMS, AND A METAL SOAP OF IN THE RANGE OF 1 TO 4 CARBON ATOMS, AND A METAL SAOP OF IN THE RANGE OF 3 TO 15 WT. PERCENT OF A HIGH NOLECULAR WEIGHT CARBOXYLIC ACID HAVING IN THE RANGE OF 12 TO 30 CARBON ATOMS PER MOLUVULE, THE WEIGHT PRECENTAGES BEING BASED ON THE TOTAL GREASE COMPOSITION, THE METAL CONSTITUENT OF SAID METALS SALTS AND SOAP BEING AN ALKALINE EARTH METAL AND SAID COMPLEX BEING FORMED AT A COMPLEX-FORMING TEMPERATURE IN THE RANGE OF 400* TO 550*F. 